The purpose of the proposed research is to investigate the response of the catecholamine and acetylcholine-mediated alterations in the metabolism of specific structures in the brain, including alterations in cyclic nucleotide and protein biosynthesis, during the development and persistence of tolerance and dependence in animals with chronic narcotic agonist encounter. Rats will be used in most studies, with parallel studies in select cases using mice of various strains. Microinjection of narcotics into select brain sites will permit the measurement of effects on neurotransmitter and cyclic nucleotide metabolism in the injected sites and in functionally related neural nuclei. Microdissected structures from acute and chronically treated animals will be employed for in vitro assays of adenylate cyclase activity in the absence or presence of antagonist narcotics, neurotransmitters, prostaglandins and the endogenous morphine-like peptide found in the mammalian brain. Similar structures will be utilized for the preparation by affinity chromatography of purified messenger RNA from variously treated animals for in vitro translation into peptides in a reconstituted polysomal system. This will permit the detection of changes in protein synthesis that may mediate the development of tolerance or the maintenance of dependence. BIBLIOGRAPHIC REFERENCES: Bonnet, K.A. and S. Gusik, Enkephalin and morphine: Brain adenylate cyclase effects and calcium ion. Trans. Amer. Soc. Neurochem. 8:82 (1977). Ehrlich, Y.H., E. Brunngraber and K.A. Bonnet. Protein phosphorylation in neostriatal membranes after narcotic exposure. Trans. Amer. Soc. Neurochem. 8: 84 (1977).